Method in the manufacture of an exchanger packing and exchanger packing manufactured according to said method



March 7, 1967 c. G. MUNTERS 3,307,617 METHOD IN THE, MANUFACTURE OF ANEXCHANGER PACKING AND EXCHANGER PACKING MANUFACTURED ACCORDING TO SAIDMETHOD Filed Jan. 28, 1963 2 Sheets-Sheet 1 FIG.

F76: 2. INVENTOR CARL GEOHG MUNTERS March 1967 .c.'G. MUNTERS 3,3 ,6 7

METHOD IN THE MANUFACTURE OF AN EXCHANGER PACKING AND EXCHANGER PACKINGMANUFACTURED ACCORDING TO SAID METHOD Filed Jan. 28, 1965 v 2Sheets-Sheet 2 INVENTOF CARL GEO/7G MU/V 755's United States Patent3,307,617 METHOD IN THE MANUFACTURE OF AN EXCHANGER PACKING ANDEXCHANGER PACKING MANUFACTURED ACCORDING TO SAID METHOD Carl GeorgMunters, 3 Danderydsvagen,

Stocksund, Sweden Filed Jan. 28, 1963, Ser. No. 254,131

Claims priority, application Sweden Jan. 30, 1962, 999/62 1 Claim. (Cl.16510) This invention relates to improvements in the manufacture ofexchanger packings and also to exchanger packings manufactured withutilization of said improvements.

More particularly this invention relates to a method in the manufactureof an exchanger packing composed of elements, such as thin layers orsheets which directly or possibly indirectly by means of distance piecesbear against one another at mutually spaced places and therebetween formpassages open from end to end and extending through the packing. Of thelayers usually at least every second is corrugated, the places of mutualcontact of the layers being formed by the ridges of the corrugations.

For utilization in an important field of application of the inventionthe layers are to advantage constituted of sheets or foils of a fibrousmaterial which preferably is non-metallic and inorganic as is the casewith asbestos. An essential field of use of the invention is thetransfer of moisture and/ or heat, in particular between two aircurrents. For this purpose the exchanger packing preferably has thestructure of a rotor adapted to move along a closed path between twopass-ages t-ransgressed by the two air currents.

One main object of the invention is to provide an exchanger packing inwhich the layers have high mechanical strength, especially in wetcondition which latter condition is actual when the exchanger packingduring its operation comes into contact with a liquid such as water.

Another object of the invention is to provide an exchanger packingpossessing hygroscopic properties and a high drying effect. These twoobjects may be aimed at by the exchanger packing of the invention eitherseparately or in combination.

It is known in prior art to increase the wet strength of sheets of afibrous material by treating with substances which together produce anonsoluble deposit of calcium silicate on the sheets or the fibresthereof. On the other hand there are used in moisture exchangershygroscopic water-soluble salts, primarily lithium compounds. It hasalso been proposed to provide silica gel in a finely divided, solid formon the layers of an exchanger packing.

The invention involves such a processing which has as its distinctivefeature of impregnating the layers with a composition of matter inliquid state of such kind as to form a gel which thereupon isconcentrated by evaporation until a solid substances remains on thelayers. According to a particular important embodiment of the inventionthe composition of matter is of a kind containing silicon or a silicicacid compound so that the deposit remaining after the concentration isconstituted by a silicon dioxyde substance. If the layers are of afibrous material such as asbestos which in itself has an insuflicientwet strength, the impregnation according to the invention imparts to thelayers a fully sufficient strength. Due to the fact that the solidsubstance such as silicon dioxyde is precipitated from a liquid inintimate contact with the fibres to constitute a gel this latter isdistributed over the fine fibres in a molecular state or condition andthereby forms a homogeneous reinforcement of the carrier fibres.

3,307,617 Patented Mar. 7, 1967 The deposit of silicon dioxyde on thelayers remains hygroscopic in a heat treatment up to a predeterminedvalue, which means that it gets similar properties as silica gel andtherefore even alone may constitute the hygroscopic constituent in anexchanger packing for transfer of moisture or heat and moisture. Due tothe particularly thin and even deposit on the fibres which deposit,moreover, is porous so that a very large surface of contact is obtainedbetween the moisture-active solid sub stance and the air, the dryingeffect calculated on the volume or the density of the exchanger packingbecomes very high. In the same degree as the heat treatment is effectedat increased temperature, the silicon dioxyde substance in its solidcondition becomes more stable. Whereas a heat treatment at a lowertemperature, such as at 200 C. or therebelow imparts to the silicondioxyde a reversible function so as to some extent to be restorable intoits gel condition it will at 'a higher temperature such as up to 600 or700 C. be more and more anhydrous and at the same time stable as to itscomposition. In other words the silicon dioxyde will no longer becapable but to a limited degree to pick up moisture, but it is at thesame time practically water-insoluble. A deposit of silicon dioxydeobtained by a heat treatment exceeding 200 C. has surprisinglyexperience to give to a moisture exchanger packing the capacity ofdehumidifying air to lower continuous absolute and relative moisturecontent than hitherto possible to obtain by use of the most effectivehygrosdopic salts such as lithium chloride. This valuable effect whichin particular is of deciding importance for some kinds of airconditioning appears at least partly to reside in the feature that thesilicon dioxyde deposit causes more favourable conditions for theintercalation of the salt crystals on the layers of the exchangerpacking or the fibres of said layers.

Other objects and advantages inherent in the invention will becomeapparent from the following description when taken in conjunction withthe accompanying drawing which shows, by way of example, the inventionapplied to a rotary transferrer of heat and/ or moisture.

In the drawing:

FIGURE 1 is a section taken along the line II of FIGURE 2.

FIGURE 2 is a section taken along the line IIII of FIGURE 1. I

FIGURE 3 shows the apparatus in external projection partly in sectiontaken along the line III-III of FIG- URE 2.

FIGURES 4 and 5 are fragmentary sections showing alternative forms ofconstruction of the rotor mass.

Referring to the drawings reference numeral 10 indicates a casing whichmay be connected to a horizontal support by means of a flange 12. Themotor 14 may be mounted directly on the casing 10 and is provided with ashaft 16 which rotates in the sleeve 18 extending inwardly from thecasing. The sleeve supports the rotor, generally indicated at 20, andmay have a hub portion 22 and a rim portion 24 between which a spirallywound web is supported. The web is preferably made of nonmetallicfibrous sheet material, such as cellulose or asbestos paper and the likeof of paper modified by asbestos fibers, glass fibers, plastic fibersand others.

The sheets may be as thin as millimeter. Preferably, the motor orsorption mass is built up to form alternate flat sheets 30 andcorrugated sheets 32 shown in FIGURE 5 of the drawing. It may also becomposed of sheets 26 spaced apart by ridges 28 as shown in FIG- URE 4or may have a honeycomb form.

The distance between the fiat sheets, or in other words, the height ofthe corrugations in sheet 32 may vary for particular conditions ofapplication. The closer the spacing of the sheets 30, the :greatersurface area per unit of 6) volume of the exchanger packing and thegreater becomes the transfer co-efiicient. The fiat and corrugatedsheets 30 and 32 divide the packing into a plurality of closely adjacentcells or passages open at both ends at opposite sides of the wheel andextending axially therethrough.

When the packing is used in an air conditioning system, as a transferrerof thermodynamic characteristics of air, the fiat sheets may be spacedfrom one another less than 3 milimeters and preferably less than 2millimeters.

The wheel 20 when acting as moisture transferrer is rotated at a veryslow rate of speed, such as on the order of l to 10 revolutions perhour. When the Wheel is used as a heat transfer element, it is rotatedat a much higher speed.

As shown in FIGURE 2, one of the air streams, such as that from anenclosure, is impelled through the duct 34 into the compartment 36 bymeans of the fan 36 and blown through the passages or cells formed bythe flat and corrugated sheets 30 and 32, into the compartment 37 andhence exhausted through the duct 38.

Another air stream, such as outdoor fresh air, is drawn by fan 44through the duct 40 into the compartment 39, through the passages of theWheel 20 at the right hand half thereof and counter current to the airstream flowing through the passages in the left hand half of the wheel;hence into compartment 41 and through the duct 42 to the enclosure to beconditioned.

The compartments 35 and 41 are separated from one another by means of apartition 46- (FIGURE 3) while compartments 37 and 39' are separatedfrom one another by means of partition 4%. Partition 4% may be attachedto a cover which can be removed to provide access to the wheel. Thewheel may be removed from the casing by first unscrewing the nut 52 fromthe shaft 16.

In order to counteract leakage of air between the compartments,stationary sealing elements 54- and 56 may be arranged in the casing atthe faces of the wheel. In the example shown in the drawing, thesesealing elements comprise a corrugated structure having large passagesrelative to the passages in the rotor mass.

However, sealing elements may also be mounted on the edges of thepartitions 46 and 48 to bear against the faces of the wheel. Suchsealing elements may be in the form of shoes mounted on the edges of thepartitions 46 and 48 and yieldingly pressed against the sides of thewheel.

The bonding together of the sheets or foils at the places of contact maybe effected by means of conventional methods and glueing agents,preferably of inoganic kind such as water glass. The bonding may even atleast partially be made by means of the gel. If the packing is assembledof so-called single-well webs which are wound in layers one upon theother the one plane and one corrugated strip of the web may be bondedtogether by means of water glass or the like in the machine formanufacture of single-well. The individual webs of the assembledsingle-well web structure may then be glued to one another by thetreatment according to the invention.

If desired the layers may be constituted by a carrier of a ceramic,possibly porous material which has been heated to sintering temperatureso as to obtain a solid, coherent structure.

The impregnation according to the invention may according to oneembodiment of the invention be carried out by means of an organicsilicic acid compound, preferably ethyl silicate or silicic acid esters.When such compound is brought into contact with or absorbs moisture itassumes a gel-like state. Thus the layers or sheets of the exchangerpacking are covered with the compound and thereupon exposed to theaction of the moisture. Simultaneously with the formation of the gelalcohol escapes. When the formation of the gel is finished watercommences to be driven out from the gel and gradually a solid covercomes into existence. This cover contains silicon dioxyde and somewater. This process is accelerated by increase of the temperature. Up tosome predeterminable temperature the solid cover may be restored to thegel state by picking up of water to some extent, but by further increaseof the temperature the silicon dioxide assumes a more and moreirreversible state and thus becomes stable.

According to another method, hereinafter to be denominated as the acidmethod, the layers, such as the asbestos sheets are initiallyimpregnated with water glass and subsequently with an acid such ashydrochloric acid or sulfuric acid whereby a gel is produced as aproduct of a chemical reaction. Residues of the acid and other solublereaction products are removed by rinsing with water provided that thecover of gel on the sheets permits it. The gel may be subjected to apartial drying treatment prior to said rinsing procedure. The gradualconcentration of the gel by evaporation is continued in the same manneras described hereinbefore.

The reinforcement imparted to the fibrous carrier is dependent on theglueing capacity of the precipitations on the fibers, said capacitybecoming better with increase of the quantity of silicon contained inthe starting substances for the impregnation. The proportion between thesilicon and alkaline constituents in the water glass must be of an orderof magnitude of at least 3:1, especially in the acid method. This doesnot imply that the concentration of the two substances necessarily mustbe high; rather diluted water glass may be used. At all events the acidconcentration must be so high that the silicon dioxide cannot takecolloidal state instead of being formed as a gel.

As is evident from the preceding explanations the solubility in water ofthe precipitated silicon dioxide is in relation to the reversibility ofthe capacity to pick up water imparted to the silica gel. Aconcentration by evaporation of the gel at relatively low temperaturesincreases the water-solubility. A concentration by evaporation atrelatively high temperatures reduces the Watersolubility but also thestrength and the glueing capacity. This implies that the precipitatedsilicon dioxide becomes brittle or fragile upon treatment at hightemperatures, in particular when all water has been stripped. As far asthe mechanical strength of the individual layers is of importance onemust always adjust the upper limit for the heat treatment to apredetermined value so as to meet the requirements of mechanicalstrength.

Usually sodium water glass is used even if potassium water glass maycome into consideration. Potassium water glass produces together withsulfuric acid as a reaction product potassium sulfate which isdistinguished from sodium sulfate by not containing any crystal water.When it is desired to avoid deformations of the exchanger packing causedby stripping of crystal water from reaction products possibly notremoved by the rinsing procedure the use of potassium water glass may beof advantage.

As may be seen from co-pending patent application Serial No. 164,880filed January 8, 1962, asbestos sheets often contain not only filamentsof asbestos but also a bonding agent for the fibres of organic naturesuch as starch, for example. In the utilization of the present inventionit may be desirable to remove these organic substances in order toeliminate the risk of fire. According to the patent an oxidation ordegassing of the organic bonding agents is performed under whichprocedure attention must be paid to the temperature in the asbestosfibres which temperature must not be increased so much as to cause themto set their crystal water free and therewith to lose their mechanicalstrength. Such a treatment may without difiiculty be combined with thetreatment according to the present invention, the stabilization of thedeposit of silicon dioxide on the fibres being. effected simultaneouslyat a highest possible temperature below the temperature critical for theasbestos fibres.

While one more or less specific embodiment of the invention has beenshown and described, it is to be understood that this is for purpose ofillustration only, and that the invention is not to be limited thereby,but its scope is to be determined by the appended claim.

What I claim is:

The method of increasing the moisture adsorptive capacity and structuralstrength of an annular heat and moisture exchange rotor body havingcellular air spaces extending from end to end formed of layers ofcorrugated sheets of asbestos comprising wetting the assembled laminatedcorrugated sheet body with an aqueous solution of water glass to effecthomogeneous concentrated impregnation of the assembled sheets and fibersthereof with the Water glass, and then reacting said water glass in situin the impregnated body with acid to convert the same to solid silicagel bonding the same structurally firm, 15

Washing out the acid and drying said body at a temperature above about200 C. and below about 700 C. to convert said body to structurally rigidhighly moisture adsorptive form.

References Cited by the Examiner UNITED STATES PATENTS 1,839,168 12/1931Stampe 117169 1,976,875 10/ 1934 Connolly et a1. 2,399,981 5/1946 Britt.2,989,418 6/1961 Harbaugh 117-16'9 X FOREIGN PATENTS 629,879 10/ 1961Canada.

5,254 1895 Great Britain. 6,944 1899 Great Britain. 554,15 6' 6/ 1943Great Britain.

MEYER PERLIN, Primary Examiner.

CHARLES SUKALO, ROBERT A. OLEARY,

Examiners.

A. W. DAVIS, Assistant Examiner.

